Propylene glycol monomethyl ether (PGME) is widely used as a solvent in numerous commercial products. Its chemical synthesis leads to the formation of two isomers: alpha and beta, the latter being usually present in the range of 0.5-1.5%. Isomer alpha has been shown to be of low toxicity. Isomer beta raises concerns as to its reproductive and developmental effects. We evaluated the reproductive and developmental toxicity of two different commercial mixes of PGME (Mix A: 99% isomer alpha and 0.5% isomer beta, Mix B: 98.5% isomer alpha and 1.5% isomer beta) on Sprague-Dawley rats. The use of two mixes allowed us to differentiate between isomer alpha and isomer beta effects. Male and female rats were exposed through drinking water to mixes A or B during a gametogenesis cycle (64 days for males and 15 days for females) to 0, 2, 5, 10 and 15% (v/v) of each mix. These animals (F0) and the three following generations (F1, F2 and F3) were followed. We observed a statistically significant decrease in the number of pups in isomer alpha-treated animals of generation F1 and a nondose-related variation of the sex ratio in F1 and F2 generations after PGME mix B treatment. The most important effect observed was a decrease in testicular and epididymal sperm counts in relation to PGME isomer beta in acute daily exposure, on the first parental generation. The effect evidenced on sex ratio needs further work in order to assay the potential persistent effects of PGME exposure.